Pneumatic seismic source



Aug. 20, 1968 a. LOPER 3,397,755

PNEUMATIC SEISMIC SOURCE Filed March 14, 1966 5 Sheets-Sheet 1 oPRESSURE INVENTOI? GEORGE B. LOPER Aug. 20, 1968 G. s. LOPER PNEUMATICSEISMIC SOURCE 3 Sheets-Sheet 2 Filed March 14, 19136 SOURCE OFPRESSUR|ZED AIR INVENTOR GEORGE B. LOPER BY M 79m Aug. 20, 1968 5. 8.LOPER 3,397,755

PNEUMATIC smsmc souncm Filed March 14, 1966 3 Sheets-Sheet 3 SUPPLY UMP/FUE AIR COMPRESSOR INVENTOR GEORGE B. LOPER Qwyam United States Patent3,397,755 PNEUMATIC SEISMIC SOURC George B. Loper, Duncanville, Tex.,assignor to Mobil Oil Corporation, a corporation of New YorkContinuation-impart of application Ser. No. 354,083, Mar. 23, 1964. Thisapplication Mar. 14, 1966, Ser. No. 534,130

19 Claims. (Cl. 1 81.5)

ABSTRACT OF THE DISCLOSURE This application is a continuation in part ofapplication Ser. No. 354,083, filed March 23, 1964, now abandoned.

This invention relates to seismic surveying and more particularly to aseismic source useful in marine seismic surveying.

In seismic exploration of underwater formations, seismic disturbancesare generated in water from a boat for the production of acoustic pulseswhich are reflected from subsurface interfaces and detected for theproduction of seismic record sections. In one system now in use, theseismic disturbances are generated by repetitively exploding acombustible mixture of air, pure oxygen, and propane in a reactorchamber having an open end coupled to Water.

In accordance with the present invention, there is provided a uniqueseismic source useful in marine seismic surveying. The source comprisesa primary chamber formed of rigid wall structure having a normallyclosed outlet end to be immersed in water. Valve means is provided foropening and closing the outlet end. In addition, means is provided forintroducing a fluid in the chamber when the valve means is in a closedposition to form a fluid pressure therein substantially greater than thehydrostatic pressure of the water at the outlet end. When the pressurewithin the chamber reaches a desired maximum value, the valve isactuated to open the outlet end to allow the pressurized fluid in thechamber to escape into the water to generate an acoustic pulse.

In one embodiment, the fluid employed for pressurizing the chamber isair. In a further embodiment, a combustible fluid such as diesel fuel isintroduced in the chamber and ignited to create a high gas pressure inthe chamber upon combustion. In the latter embodiment, the valve isactuated to open the outlet end when the pressure within the chamberincreases to a desired maximum value above the hydrostatic pressure ofthe water following ignition.

The system of the present invention thus eliminates the need for pureoxygen and propane which are diflicult to acquire in certain areas ofthe world where seismic exploration now is being carried out. The systemof the present invention also has advantages in that it presents littleif any fuel storage problem since air is readily available as well asdiesel fuel from the boats fuel supply.

In the system of the present invention as disclosed, the release of thepressurized gas from the chamber results in the formation of a largeexpanding gas bubble which encompasses the outlet end of the chamber.While the bubble still encompasses the outlet end, the valve is moved toa closed position to prevent water from subsequently entering thechamber. Thus, the chamber is maintained free of water and may beemployed repetitively to generate acoustic pulses at short timeintervals.

In accordance with a further aspect of the present invention, means isprovided for employing the fluid pressure within the primary chamber tomaintain the valve closed for a desired time period. In addition, meansis provided for employing fluid pressure to actuate the valve means toopen the outlet end.

In a more specific aspect, the valve comprises a spoolshaped memberhaving first and second rims coupled together by an interconnectingmember. At least the second rim of the valve is sup'ported for movementwithin the primary chamber. Means is provided for moving the valve to aclosed position wherein the first rim closes the outlet end of thechamber. In the closed position, at least a portion of the inner surfaceof the first rim forms a portion of the interior Wall surface of thechamber and the outer surface thereof is exposed to the water. The areaof the projection of the inner surface of the second rim onto a planenormal to the axis of the valve is greater than the area of theprojection of the inner surface portion of the first rim onto the sameplane. Thus, the second rim has a greater inner surface area than thatof the first rim for the application of fluid pressure parallel to thevalve axis. In addition, means is provided to form a second chamber withthe outer surface of the second rim when the valve is closed. Thischamber norm'ally is maintained at a relatively low pressure. Thus, whenthe valve is moved to a closed position and the primary chamber ispressurized, a net force is exerted on the valve, by the fluid pressure,in a direction opposite the outlet end, thereby maintaining the valveclosed. When it is desired to generate an acoustic pulse, the secondchamber is exposed to an increased pressure. In this manner, additionalforce is applied to the valve to overcome the net force on the valve,mentioned above, thereby forcing the valve to an open position torelease the pressurized gas from the primary chamber.

'For further objects and advantages of the present invention and for amore complete understanding thereof, reference may be had now to thefollowing detailed description taken in conjunction with theaccompanying drawings wherein:

FIGURE 1 schematically illustrates a seismic source of the presentinvention;

FIGURE 2 illustrates curves useful in understanding the presentinvention;

FIGURE 3 illustrates in detail one embodiment of the present invention;

FIGURE 4 illustrates an enlarged cross section of the system of FIGURE 3taken along the lines 4--4 thereof;

FIGURE 5 illustrates in detail another embodiment of the presentinvention;

FIGURE 6 illustrates in part a cross section of the system of FIGURE 5taken along the lines 6-6 thereof; and

FIGURE 7 illustrates a modification of the system of FIGURE 5.

Referring now to FIGURE 1, the seismic source of one embodiment of thepresent invention for generating acoustic pulses comprises a chamber 10supported in water from a boat by cable 11 and having an outlet end 12coupled to the Water. A quick-opening valve, herein illustrated asspool-shaped valve 13, is provided for opening and closing the outletend. Fluid is introduced in the chamber by means, not shown in FIGURE 1,to create a high fluid pressure within the chamber. At a desired time,the valve 13 is actuated to allow the pressurized fluid to escape intothe Water in a minimum of time. The pressure in the water thus quicklyincreases to a maximum value for the pro- 3 duction of a pressure pulse,as illustrated at time a in FIGURE 2, and from which the acoustic pulseis derived.

In the system of FIGURE 1, the fluid injected is a gas, such as airinjected under pressure, to create a high gas pressure within thechamber for the production of an acoustic pulse. In a furtherembodiment, to be described hereinafter, a combustible fluid such asdiesel fuel is introduced in a closed chamber and ignited to create ahigh gas pressure within the chamber. A quick-opening valve is actuatedto release the pressurized gas at a desired time following ignition forthe production of an acoustic pulse. In the operation of the systems ofthese embodiments, a large gas bubble, illustrated at 13' in FIGURE 1,is formed subsequent to the release of the pressurized gas into thewater. The formation of the bubble produces a negative pulse, asillustrated at time b in FIGURE 2, and normally a secondary pressurepulse, as illustrated at time c of curve A. As will be describedhereinafer, means is provided for reducing the amplitude and frequencyof the secondary pressure pulse as i'lustrated by curve B.

Referring again to FIGURE 1, the air pressure within the chamber isemployed to maintain the valve in a closed position as the pressureincreases to a desired maximum value and further to actuate the valve toopen the outlet end. More particularly, the spool-shaped valve comprisesa first rim 14 coupled by interconnecting member 15 to a second rim 16.The valve is moved to a closed position (by means not shown in FIGURE 1)wherein rubber O-ring and seat 17 engages the inner surface 18 of rim 14to seal the outlet end. The inner diameter of O-ring 17 is slightly lessthan the diameter of the upper rim 16. Thus, rim 16 has a larger innersurface area for the application of fluid pressure parallel to the valveaxis. When the valve is in a closed position, rubber O-ring and seat 20,provided in member 21, engages the upper surface 22 of rim 16 to form anannulus or chamber 23 sealed from chamber The pressure within thechamber 23 normally is maintained (by means not shown in FIGURE 1) at avalue less than the pressure within the chamber 10 and, in fact, nearatmospheric pressure. Hence, as the chamber 10 is pressurized, a netupward force is exerted on the valve 13, thereby maintaining the valvein a closed position. When it is desired to generate an acoustic pulse,solenoid valve 24 is actuated to allow the pressurized gas withinchamber 10 to pass into chamber 23. Thus, additional force is applied tothe upper surface 22 of rim 16 to overcome the net upward force on thevalve 13, thereby breaking the seal between the chamber and the valve.The pressurized air in chamber 10 then acts to force the valve 13downward in a minimum of time and thus is rapidly released into thewater to generate an acoustic pulse. Container 25 is provided to stopthe valve after it has traveled downward sufficiently to allow thepressurized gas to escape. More, particularly, as the rim 14 of valve 13approaches and enters container 25, the water therein acts to brake themovement of the valve.

Referring now to FIGURE 3, there will be described in more detail thesystem of FIGURE 1, wherein pressurized air is introduced in the chamberfor the generation of acoustic pulses. Like elements have been givenlike character references as employed in FIGURE 1. The valve 13 issupported for reciprocation relative to chamber 10 by means includingsupport member 30 and bearing means 31. O-ring 17 is supported in member32 which forms the outlet end. This member, coupled to the lower end ofthe chamber '10, is provided for ease of assembly and disassembly of thesystem. O-ring 33 provides a seal between member 32 and the lower end ofchamber 10.

The assembly 21 for supporting O-ring 20 is supported by rods 33' (alsoillustrated in FIGURE 4) and coupled to member 32. The assembly 21comprises a first diskshaped member 34 coupled to rods 33' and a seconddiskshaped member .35 of smaller diameter and which extends below member34 between rods 33. The O-ring 20 is supported in a ring-shaped member36, also illustrated in 4. FIGURE 4, which is biased downward by aplurality of springs 37. These springs are positioned in apertures 38(FIGURE 4) formed in member 36 and are provided to urge the member 36and hence the O-ring 20 toward the top surface 22 of rim 16. Thisarrangement is provided to insure that the O-ring 20 engages surface 22at the same time that O-ring 17 engages surface 18 even though thedimensions of the O-rings may change due to usage, thereby maintainingthe proper seal between the O-rings and the respective surfaces. AnO-ring 39 is provided between members 35 and 36 to maintain a sealtherebetween.

When the valve 13 is in the closed position, the chamber 23 formed isvented to the atmosphere to prevent the pressure in chamber 23 frombuilding up if leakage occurs between the seals. In this respect, a flowpath extends from chamber 2 3 to the surface by way of conduit 40,aperture 41 formed in one of the rods 33', aperture 42 formed in member32, and conduit 43 extending to the surface.

The system for moving the valve 13 to a closed position comprisesconduit 50 fixedly secured to members 34 and 35 and extending downwardinto a chamber 51 formed in connecting member 15. Valve '13 movesrelative to conduit 50 and is moved upward from a downward position byinjecting compressed air into chamber 51 by way of conduit 50 andaperture 52. The compressed air pushes against the upper surface ofchamber 51 to move the valve 13 upward. Air is injected into conduit 50by way of a flow path comprising conduit 53, aperture 54 formed in oneof the rods 33', aperture 55 formed in member 32, and conduit 56extending to the surface to a compressed air source 57. O-rings 57' areprovided in rim 16 and the bottom end of conduit 50 to maintain a properseal between the conduit and valve 13. In addition, bearing members 58are provided in rim 16 and the bottom end of conduit 50 to enable thevalve 13 to slide relative to conduit 50.

The system preferably is cyclically operated whereby acoustic pulses arerepetitively generated, for example, at a repetition rate of one pulseevery six seconds. A plurality of cams 60-63 driven by motor 64sequentially actuate switches 6568 within each cycle to control thevarious components of the system to generate an acoustic pulse. Thesequence of operation during a cycle now will be described assuming thatan acoustic pulse has just been generated and that the valve 13 is in anopen position. At this time, solenoid valve 24 within chamber 10 isclosed as well as solenoid valves 69-71 employed for controlling theflow of air into and out of chamber 10.

As mentioned previously, the release of the pressurized air into thewater results in the formation of a large air bubble and whichcompletely encompasses the outlet end 12 of chamber 10. While the bubblestill encompasses the outlet end 12 and prior to the time the bubbledrifts away, the valve 13 is moved to a closed position to prevent thewater from entering the chamber 10. More particularly, cam 60 firstcloses switch 65 to open valve '69 to allow pressurized air from supply57 to pass into chamber 51 to move the valve 13 to a closed position.Cam 61 next closes switch 66 to open valve 70 to allow pressurized airfrom source 57 to flow, by way of conduit 72, into chamber 10. After thepressure within the chamber 10 is sufficient to maintain valve 13 in theclosed position, cam 60 allows switch 65 to open, thereby stopping theflow of air into chamber 51. Simultaneously, or at a short timeafterward, cam 62 closes switch 67 to open solenoid valve 71 to ventchamber 51 to the atmosphere by way of conduit 56, conduit 73, and openvalve 711. When the pressure in chamber 10 increases to a desiredmaximum value, cam 61 allows switch 66 to open, thereby allowing valve70 to close to stop the flow of air into chamber 10. In addition, cam 62allows switch 67 to open to close valve 71. Finally, cam 63 closesswitch 68 to open valve 24 in chamber 10 to allow pressurized gas tofiow from the chamber 10, by way of conduit 74, into chamber 23 toactuate the valve for the generation of an acoustic pulse. The innerdiameter of .conduit 40 is smaller than that of conduit 74 and theopening of the valve 24. Thus, the pressure in chamber 23 .builds up toa value suflicient to overcome the net upward force on valve 13, therebybreaking the seal between the chamber and the valve. The pressurized airin chamber then forces the valve 13 downward in a minimum .of time andis rapidly released into the water to generate an acoustic pulse.

. .'In one embodiment, the valves 24 and 69-71 were spring-biased,solenoid-actuated valves. The rim 16 of valve 13 had a diameter of seveninches. The O-ring 17 had an inside diameter of 5% inches and an outsidediameter of 6% inches. The outside diameter of connecting member was twoinches. In addition, the O-ring 20 had an inside diameter of 6% inchesand an outside diameter of seven inches. The outside diameter of conduit50 was the release of the pressurized gas into the water. One systemwhich may be employed to reduce secondary pressure pulses is disclosedand claimed in my copending application Ser. No. 574,244, filed Aug. 22,1966, which is a continuation of application Ser. No. 353,874, filedMar. 23, 1964, now abandoned, entitled System and Method for MarineSeismic Surveying and assigned to the same assignee as the presentinvention. This system will be described briefly in connection withFIGURE 1 and comprises a plurality of conduits 80 provided to presentflow paths between the bubble formed and the surface. The upper ends 81of conduits 80 are open to the surface and .the lower ends 82 arepositioned to break into the bubble as it expands. Valves 83 areprovided normally to maintain the lower ends closed to maintain theconduits 80 substantially free of water. The valves are opened when thebubble encompasses the lower ends of the conduits to present a pluralityof flow paths between the bubble and the surface to prevent theformation of high pressures in the bubble subsequent to expansion.

At certain depths at which seismic disturbances are generated in seismicexploraiton, the internal pressure of the bubble decreases belowatmospheric pressure. Under these conditions, valves 83 are opened whenthe internal pressure of the bubble decreases to a certain value belowatmospheric pressure to allow air from the surface to pass into thebubble. In this manner, the amplitude of bubble oscillation is reducedthereby reducing secondary pressure pulses.

As described in my copending application, mentioned above, springs areprovided to control the opening and closing of the valves. Referring toone of the conduits 80 (FIGURE 1), valve 83 is pivoted at 84 and biasedto a closed posit-ion by spring 85. When the pressure in the bubble 13'decreases to a certain value below atmospheric pressure, the pressure onthe top surface of the valve becomes suflicient to overcome the upwardforce applied by the spring to push the valve to an open position.

-Referring now to FIGURE 5, there will be described another embodimentof the present invention wherein a combustible fluid such as diesel fuelis introduced in a chamber 100 and ignited to create a high gaseouspressure therein upon combustion. When the pressure reachessubstantially a maximum value, a quick-opening, spoolshaped valve 101 isactuated to open the outlet end 102 of the chamber to allow thepressurized gas to escape duction of acoustic pulses. In the system ofFIGURE 5, diesel fuel and air are separately injected into the chamberwhere a combustible mixture is formed and ignited. Compressed air firstis injected into the chamber from air compressor 103 by way of conduit104 and check valve 104. Next, diesel fuel under pressure is sprayedinto the chamber, for a short period of time, from a plurality ofnozzles 105 also illustrated in FIGURE 6. The diesel fuel is mixed withthe pressurized air in the chamber to form a combustible mixture whichis ignited by heating elements 106. Upon ignition of the combustiblemixture of diesel fuel and air, the pressure within the chamberincreases. As the pressure increases to a maximum value, solenoid valve107 is opened to actuate the spool-shaped valve 101 for the generationof an acoustic pulse as now will be described.

Spool-shaped valve 101 has a lower rim or piston-type head 108 coupledby connecting member 109 to an upper rim or piston-type head 110. Thelower head 108 reciprocates in a lower piston cylinder 111 and has ametal seal ring 112 coupled thereto to form a seal between the outletend 102 of chamber 100 and valve 101 when the valve is in a closedposition. Similarly, the upper head reciprocates in an upper pistoncylinder 113 and has a metal sea-l ring coupled thereto to form a sealbetween member 115 of chamber 100 and the upper head when the valve isclosed. The upper head 110 is of slightly larger diameter than the lowerhead 108, thereby having a larger inner surface area for the applicationof fluid pressure parallel to the valve axis. The relative diameters ofthe two heads are shown more clearly in FIGURE 6 wherein the outerboundary of upper head 110 is illustrated by dotted line 110 forcomparative purposes. A return spring 116 is provided to urge the valve101 toward a closed position as will be described hereinafter. When thevalve is closed, an annulus or chamber 119 sealed from chamber 100 isformed between the top flange 120 and the upper surface 121 of the upperhead 110. This annulus or chamber is vented to the atmosphere by smallconduit 122. Thus, when the chamber is pressurized and the valve 101 isclosed, there will be a net upward force on the valve which tends tohold the valve in a closed position. As the pressure within chamber 100reaches its peak value upon ignition of the combustible mixture offluids introduced therein, solenoid valve 107 is opened to allowpressurized gas within chamber 100 to be applied by way of conduits 123and 124 into the annulus 119. When the pressure in annulus 119 becomessuflicient to overcome the return spring force and the force createdbecause of the different valve head sizes, the valve 101 will start tomove in a downward direction. In addition, when the seal ring on theupper valve head 110 passes over the ports 125 formed in the upperpiston cylinder 113, the pressure on both sides of the valve head willbe more or less equalized. Thus, a large downward force is exerted onthe valve 101 by the pressurized gas in the chamber. As the seal ring onthe lower piston head passes over the vent ports 126 formed in the lowerpiston cylinder, the pressure in the chamber 100 is released into thewater for the production of an acoustic pulse. The valve is stopped by ahydraulic shock absorber comprising braking container 127 and is pushedclosed by return spring 116. Hydraulic shock absorbers comprisingchambers 128, springs 129, and members 129 provided at the top slow thevalve return while closing.

The system for injecting diesel fuel into chamber 100 by way of nozzles105 comprises an accumulator 130 into which diesel fuel is pumped underpressure by pump 131 coupled to fuel supply 132. Accumulator 130 in turnis'coupled to nozzles 105 by way of manifold 133 and conduits 134, alsoillustrated in FIGURE 6. The pressurized diesel fuel is injected intochamber 100 only for a short time period to form a desired combustiblemixture. Conduits 134 all have the same lengths to insure that the 7same amount of fuel is injected simultaneously through all of thenozzles 105.

In a further description of the system, support conduit 140 is providedto additionally support the valve 101 as well as return spring 116.Bearing members 141 are provided between support conduit 140 andconnecting member 109. Lubricating fluid is circulated between bearingmembers by conduits 142. Support rods 143 are coupled between the lowerand upper heads of the valve 101 for additional strentgh.

As in the system of FIGURE 3, the system of FIGURE is cyclicallyactuated to repetitively generate acoustic pulses. Within each cycle,cams 150-152, driven by a motor 153, actuate switches 154-156 to controlthe various components to generate an acoustic pulse. The sequence ofoperation during a cycle now will be described assuming that an acousticpulse has just been generated and that the valve 101 has returned to aclosed position. At this time, solenoid-actuated valve 107 is closed aswell as solenoid-actuated valves 157 and 158 employed for controllingthe operation of the system.

In the generation of an acoustic pulse, cam 150 first closes switch 154to open valve 157 for a predetermined period of time, thereby allowingcompressed air to flow into chamber 100. Next, cam 151 actuates switch155 to open valve 158 for a preset period of time, which may be of theorder of one-fourth of a second, after which time it closes. Asmentioned previously, diesel fuel under pressure is sprayed into thechamber 100 through nozzles 105 where it is mixed with pressurized airand ignited by heating elements 106. As the pressure increases to adesired maximum value, the time of which is determined by experiment,cam 152 closes switch 156 to open solenoid valve 107 for a short presetperiod of time. Valve 101 thus is actuated to allow the pressurized gasin the chamber to escape into the water for the production of anacoustic pulse as described previously. After the acoustic pulse hasbeen generated, return spring 116 pushes the valve 101 to a closedposition. This occurs while the resulting bubble encompasses the outletend 102 of chamber 100 and prior to the time that the bubble driftsaway.

In the system of FIGURE 5, the production in the chamber of pressures upto 500 pounds per square inch over atmospheric pressure is desirable forthe generation of acoustic pulses. The chamber 100 and valve 101preferably are formed of stainless steel. The heating elements 106disclosed may be electric coils which are continuously energized.Suitable means may be provided to flush the chamber of exhaust gases.For example, after valve 101 has closed and while valve 157 has openedduring the next cycle, other valve mechanism coupled to chamber 100 (notshown) may be opened for a short time period to allow the fresh air toflush out the exhaust gases.

In the embodiment of FIGURE 5, a mechanical spring 116 was disclosed asbeing employed for moving valve 101 to close the outlet end of chamber100 after the generation of an acoustic pulse. It is to be understood,however, that an arrangement, of the type disclosed in the embodiment ofFIGURE 3 utilizing compressed air, may be employed instead to move thevalve 101 to a closed position. Such an arrangement could include acylinder coupled to the valve 101 into which compressed air isintroduced for moving the valve upward and closed after the generationof an acoustic pulse. Suitable conduits and valve control arrangementswould be employed for controlling the introduction and release ofpressurized air into and from the cylinder as can be understood from thesystem disclosed in FIGURE 3.

In the acoustic source described above in connection with FIGURE 5, thegas pressure within the chamber 100 was employed to actuate the valve101 in the generation of the acoustic pulse. It is to be understood thatpressurized air, derived from supply formed by conduit 104 and aircompressor 103, may be employed instead to actuate valve 101. In thisalternative, electrical switch 170 8 is moved to contact terminal 171whereby a valve 172 rather than valve 107 will be controlled by switch156. When valve 172 is opened during the operating cycle, compressed airfrom conduit 104 is applied to annulus 119 by way of check valve 173 andconduits 174 and 124.

The air compressor 103 employed has a capacity sufficient to pressurizethe chamber up to 100 pounds per square inch during each operating cycleprior to the application of diesel fuel. In addition, the conduit 104employed has a relatively large volume in that its length is of theorder of 50 feet and the internal diameter is about two inches. Thus,suflicient pressure will be maintained in conduit 104 after valve 157 isclosed, for application to annulus 119, to overcome the net upward forceon valve 101 whereby it will be moved down to allow the high pressurewithin the chamber 100 to act on the top surface 121 of valve 101.

Referring now to FIGURE 7, there will be described a modification of thesystem of FIGURE 5 wherein air and diesel fuel sequentially are injectedinto the chamber 100 to form a combustible mixture which is ignited by aspark plug arrangement. More particularly, as in the system of FIGURE 5,pressurized air first is injected into the chamber. Next, diesel fuel issprayed into the chamber by nozzles for a short period of time. At thetermination of the diesel fuel injection, valve 160 is opened to allow acombustible gas, such as pressurized propane gas from supply 161, toflow by way of nozzle 162 into chamber 100. Simultaneously, with theactuation of valve 160 or shortly thereafter, spark plug 163 is actuatedby pulser 164 to ignite the propane gas to obtain a temperaturesuflicient to ignite the combustible mixture of diesel fuel and air.Solenoid valve 107 or 172 (FIGURE 5) is actuated in a manner similar tothat described in the operation of the system illustrated in FIG- URE 5to actuate the valve 101 to allow the pressurized gas in the chamber toescape into the water for the generation of an acoustic pulse.

Although only one spark plug arrangement is illustrated in FIGURE 7, aplurality of spark plugs and propane nozzles may be employed andactuated simultaneously to increase the burning rate and hence thepressure in the chamber 100.

In the system of FIGURES 5-7, diesel fuel and air were disclosed asbeing separately injected into the chamber to form a combustible mixturetherein. It is to be understood, however, that the combustible mixturemay be formed first and then injected into the chamber for ignition, forexample, by the system disclosed in FIGURE 7.

Now that the invention has been described with certain embodiments,modifications will become apparent to those skilled in the art, and itis intended to cover such modifications as fall within the scope of theappended claims.

What is claimed is:

1. An acoustic source for generating acoustic pulses in water forexploratory purposes comprising:

an annular chamber formed of means including rigid outer wall structureand having a first end and outlet port means spaced from said first endto be coupled to water, valve means including a release member supportedfor movement in a first direction away from said first end to an openposition for opening said port means and in an opposite direction towardsaid first end to a closed position for closing said port means,

means for introducing a fluid in said chamber when said valve means isin a closed position to form a high gas pressure in said chamberincluding a portion of said chamber between said first end and saidoutlet port means,

means for actuating said valve means suddenly to move said valve meansto said open position to open said outlet port means to allow thepressurized gas in said portion of said chamber to be released rapidlyinto the water to generate an acoustic pulse,

said valve means including: an elongated tubular member defined bytubular wall structure extending'from said release member andsupportedfor concurrent movement within the confines of said outer wall structureforming said chamber, and

retract means disposed within said tubular member for developing valveretract forces .wholly within said tubular member for application tosaid -valvemeans to move said valve means to said closed positionfollowing the generation of an acoustic pulse. 2. The acoustic source ofclaim 1 comprising:

wall structure means, said valve means having a first surface facingsaid wall structure means and movable toward and away from said wallstructure means upon movement of said valve means to said oppositeandfirst directions, respectively, seal means comprising resilient means atleast a portion of which is located between said wall structure meansand said first surface for compression in one of said directions uponmovement of said valve means in said opposite direction to saidclosedposition to form a pressure seal between said first surface and saidwall structure means forming a control region unexposed to said high gaspressure in said chamber, said control'region being formed within thevolume defined by said wall structure means, said first surface of saidvalve means, and said seal means, said seal means defining the outerlimits of said control region, said valve means having means to whichpressure is applied in said opposite direction to urge said valve meanstoward said wall structure means to effect said pressure seal to formsaid control region sealed from high gas pressure within said chamber,and means for increasing the gas pressure within said control region tomove said valve means to a position to eliminate said pressure seal andallow said high gas pressure to move said valve means rapidly to saidopen position. 3. In an acoustic source for generating high energyacoustic pulses in Water for exploratory purposes having: meansincluding rigid outer wall structure forming a pressure chamber withinwhich there may be developed high gas pressures and including an outletport means, valve means including a release member supported formovement in a first direction from a position closing said outlet portmeans to an open position for release of said gas pressure, 1 theimprovement which comprises:

a control element, an elongated rigid tubular member interconnectingsaid release member and said control element, said control elementhaving a first surface facing in the direction of said outlet port meansand an opposite surface facing in the opposite direction,

the effective area of'said first surface of said control element exposedto said gas pressure being greater than that of said release member,

releasing means for said release member comprising a peripheral portionof said opposite surface of said control element and associated wallstructure forming therebetween a control region sealed from said highgas pressure when said lease member to adjacent said control element,"

said tubular member including said hollow region being supported formovement within the confines of said outer wall structure forming saidchamber,

the greater area of' said control element exposed to said high gaspressure biasing said release member and said control element to theirclosed positions,

means for increasing the pressure within said control region forconcurrent movement of said release member and of said control elementfor high speed movement, of both to their open positions. by said highgas pressure, and

retract means disposed-within said hollowregion and locatedto besurrounded by said tubular wall structure and supported at least in partwithin the confines of said outer wall structure forming said chamberfor moving said release member and said control element to their closedpositions after each operation from their open positions. 7

4. The acoustic source of claim 3 wherein:

said associated wall structure is substantially closed and has a surfacearea defining the upper boundarv of said control region,

said opposite surface of said control element facing said associatedwall structure and movable away from and toward said associated wallstructure upon movement of said valve means in said firstdirection andin an opposite direction to said closed position, respectively,

said opposite surface forming the lower boundary of said control regionwhen said valve means is in said closed position,

means utilized for moving said valve means in said opposite direction tosaid closed position,

a substantially ring-shaped contact seal means comprising resilientmeans at least a portion of which is located between said associatedwall structure and said opposite surface for compression in one of saiddirections upon movement of said valve means in said opposite directionto said closed position to form a pressure seal between said oppositesurface and said associated Wall structure forming said control regionunexposed to high pressure in said chamber,

said pressure seal surrounding a portion of said opposite surface andsaid surface area of said associated wall structure defining the outerboundary of said control region,

the increase in pressure within said control region causing said valvemeans to move away from said surface area to eliminate said pressureseal and to expose said control region and hence said portion of saidopposite surface to high gas pressure to apply high. gas pressure to anincreased area of said valve means for high speed movement of said valvemeans to said open position by said high gas pressure to allow said highgas pressure in said portion of said chamber to be released rapidly intothe water to generate an acoustic pulse.

5. The acoustic source of claim 3 wherein:

said retract :means disposed within said hollow region develops valveretract forces wholly within said tubular wall structure forapplication-to said valve means for movement of said release member andsaid control element to their closed positions after each operation fromtheir open positions.

6. An acoustic source for generating acoustic pulses in water forexploratory purposes. comprising-z a'high pressure chamber having afirst. end and outlet port means spaced from said first end to becoupled to water,"

valve means including arelease. 'member'supported for movement in afirst direction away from said first end to an open position for openingsaid port means and in an opposite direction toward said first end to aclosed position for closing said outlet port means,

means for introducing a fluid in said chamber when said valve means isin a closed position to form a high gas pressure in said chamberincluding a portion of said chamber between said first end and saidoutlet port means,

wall structure means having a surface area defining the upper boundaryof a control region,

said valve means having a first surface facing said wall structure meansand movable toward and away 'from said wall structure means uponmovement of said valve means in said opposite and first directions,respectively,

said first surface forming the lower boundary of said control regionwhen said valve means is in a closed position,

means utilized for moving said valve means in said opposite direction toa closed position for closing said outlet port means and for formingsaid control region between said surface area and said first surfaceunexposed to said high gas pressure in said chamber.

a substantially ring-shaped contact seal means comprising resilientmeans at least a portion of which is located between said wall structuremeans and said first surface for compression in one of said directionsupon movement of said valve means in said opposite direction to saidclosed position to form a pressure seal between said first surface andsaid Wall structure means,

said pressure seal surrounding a portion of said first surface and saidsurface area of said wall structure means and defining the outerboundary of said control region,

control means for increasing the pressure within said control region tomove said valve means away from said surface area to expose said controlregion and hence said portion of said first surface to said high gaspressure to apply said high gas pressure to an increased area of saidvalve means for high speed movement of said valve means to said openposition by said high gas pressure to allow said high gas pressure insaid portion of said chamber to be released rapidly into the water togenerate an acoustic pulse.

7. An acoustic source for generating acoustic pulses in water forexploratory purposes comprising:

a chamber formed of means including rigid outer wall structure andhaving a first end and an outlet port means spaced from said first endto be coupled to water,

movable valve means including a release member supported for opening andclosing said outlet port means,

means for injecting pressurized air into said chamber,

a plurality of fuel injectors disposed in spaced relation around theperiphery of said chamber in two spaced planes between said first endand said outlet port means for introducing into said chamber a pluralityof streams of fuel for mixture with said air to form a combustiblemixture in said chamber,

each plane having a plurality of igniting means located therein,

said igniting means in each plane being spaced one from the other andfrom said fuel injectors and disposed around the periphery of saidchamber for igniting at a plurality of locations said combustiblemixture to form hot gases of high pressure within said chamber,

said valve means having structural means including a control meanssupported within the confines of said outer wall structure forming saidchamber and extending from said release member to a position adjacentsaid first end of said chamber and exposed to said highgas pressure whensaid valve means is in a closed position, and

means for actuating said valve means after ignition of said gasessuddenly to move said valve means to open said outlet port means toallow the high pressure gas in said chamber to be released rapidly intothe water to generate an acoustic pulse.

8. The acoustic source of claim 7 wherein:

said fuel injectors comprise diesel fuel injectors having end portionsfor directing the diesel fuel into the unobstructed space of saidchamber.

9. An acoustic source for generating acoustic pulses for exploratorypurposes while immersed in a body of water, the outer wall structurebeing in contact with the water and having water extending centrallytherethrough when said source is immersed in water comprising:

an annular chamber formed by said outer wall structure and centrallyextending tubular wall structure through which a column of water extendswhen said source is immersed in water,

said chamber having an outlet port,

said tubular wall structure including valve means for opening andclosing said port,

means for introducing a fluid into said annular chamber when said valveis in a closed position to form a high gas pressure in said chambergreater than the hydrostatic pressure of the water at said outlet port,and

means for actuating said valve means suddenly to move said valve meansto open said outlet port to allow the pressurized gas in said chamber tobe released rapidly from said outlet port to generate an acoustic pulse.

10. The acoustic source of claim 9 in which there is provided:

means for introducing a combustible fluid into said annular chamber, and

means for igniting said combustible fluid to form hot gases of highpressure in said annular chamber, which annular chamber has said columnof water passing through its central portion and is surrounded by waterwhen said source is immersed in water.

11. An acoustic source for generating acoustic pulses in water forexploratory purposes comprising:

a chamber having a first end, a spaced second end, and enclosing wallstructure therebetween defining the outer limits of a chamber regionwithin said enclosing wall structure,

said second end having an outlet port to be coupled to water,

valve means supported for opening and closing said said valve meansbeing cooperative with structure for forming a sealed annular chamberregion with a central region extending therethrough for receiving andcontaining water when said source is placed in Water and said valvemeans is in a closed position,

said valve means including a tubular member extending centrally intosaid enclosing wall structure to form said sealed annular chamber whensaid valve means is in a closed position,

means for introducing a fluid in said annular chamber region when saidvalve is in a closed position to form a high gas pressure in saidchamber region greater than the hydrostatic pressure of the water atsaid outlet port, and

means for actuating said valve means suddenly to move said valve meansto open said outlet port to allow the pressurized gas in said chamberregion to be released rapidly into the water to generate an acousticpulse.

12. An acoustic source for generating acoustic pulses in water forexploratory purposes comprising:

a chamber having first and second axially aligned ends and an outer wallstructure intermediate said ends defining the outer limits of a pressurechamber region within said outer wall structure,

said second end having an outlet port,

movable valve means having a first end for opening and closing saidoutlet port,

said valve means including a centrally located tubular member,

means for introducing fluid including combustible fluid into saidchamber when said valve means is in a closed position,

means for igniting said combustible fluid to form hot gases of highpressure in said chamber region,

means for supporting said tubular member of said valve in an axialposition within the confines of said outer wall structure of saidchamber when said valve means is in a closed position to provide a waterreceiving region which extends interiorly of said outer wall structureof said chamber and is in communication with and exposed to water whensaid source is placed in water, and

means for actuating said valve means suddenly to move said valve meansto open said outlet port to allow the pressurized gas in said chamberregion to be released rapidly from said outlet port to generate anacoustic pulse.

13. An acoustic source for generating acoustic pulses in water forexploratory purposes while immersed in water comprising:

a chamber having a first end, a spaced second end, and outer wallstructure intermediate said ends defining a pressure chamber regionwithin said outer wall structure,

said second end having an outlet port to be coupled to water,

movable valve means for opening and closing said outlet port,

means for introducing fluid in said chamber region when said valve meansis in a closed position to form a high gas pressure in said chamberregion greater than the hydrostatic pressure of the water at said outletport,

said valve means including elongated structure having an apertureextending therethrough in the longitudinal direction,

means for supporting a portion of said valve means including saidelongated structure within the confines of said outer wall structure ofsaid chamber when said valve means is in a closed position to provide aregion within said aperture which extends through said pressure chamberregion for receiving and containing water when said source is immersedin water,

said elongated structure of said valve serving as a portion of the gaspressure confining wall structure of said pressure chamber region whensaid valve means is in a closed position, and

means for actuating said valve means suddenly to move said valve meansto open said outlet port to allow the pressurized gas in said chamberregion to be released rapidly into the water to generate an acousticpulse.

14. The acoustic source of claim 13 comprising:

means for introducing a combustible fluid into said chamber region, and

means for igniting said combustible fluid to form hot gases of highpressure in said chamber region which is formed between said elongatedstructure providing said extending water receiving region and said outerwall structure.

15. The acoustic source of claim 14 comprising:

a plurality of fuel injectors and igniters spaced around said outer wallstructure of said chamber, one of each of said fuel injectors beingpositioned to inject fuel toward one of said igniters to ignite saidfuel at a plurality of locations in said chamber.

16. The acoustic source of claim 13 wherein:

said valve includes a release member for opening and closing said outletport and structure extending from said release member and movabletherewith including a tubular member interconnecting a control memberwith said release member,

said aperture extending axially through said release member, saidtubular member, and said control member,

said support means axially supporting said extending structure includingsaid tubular member Within the confines of said outer wall structure ofsaid chamber when said valve means is in a closed position to provide anannular chamber region sealed from water whose inner walls are definedby said tubular member and a central region within said apertureextending through said annular chamber region for receiving andcontaining water when said source is immersed in water.

17. The acoustic source of claim 16 comprising:

a plurality of fuel injectors and igniters spaced around said outer wallstructure of said chamber, one of each of said fuel injectors beingpositioned to inject fuel toward one of said igniters to ignite saidfuel at a plurality of locations in said chamber.

18, The acoustic source of claim 17 wherein:

said fuel injectors are disposed in spaced relation around the peripheryof said chamber in two spaced planes between said first end and saidoutlet port means,

each plane having a plurality of igniting means located therein,

said igniting means in each plane being spaced one from the other andfrom said fuel injectors and disposed around the periphery of saidchamber.

19. An acoustic source for generating acoustic pulses in water forexploratory purposes comprising:

a chamber formed of rigid wall structure having a first end and anoutlet port means spaced from said first end to be coupled to water,

movable valve measn including a release member supported for opening andclosing said outlet port means,

means for injecting pressurized air into said chamber,

a plurality of fuel injectors disposed in spaced relation around theperiphery of said chamber in two spaced planes between said first endand said outlet port means for introducing into said chamber a pluralityof streams of fuel for mixture with said air to form a combustiblemixture in said chamber,

each plane having a plurality of igniting means located therein,

said igniting means in each plane being spaced one from the other andfrom said fuel injectors and disposed around the periphery of saidchamber for igniting at a plurality of locations said combustiblemixture to form hot gases of high pressure in said chamber, and

means for actuating said valve means after ignition of said gasessuddenly to move said valve means to open said outlet port means toallow the high pressure gas in said chamber to be released rapidly intothe water to generate an acoustic pulse.

References Cited UNITED STATES PATENTS 1,789,209 1/ 1931 Asbury 251-3372,846,019 8/1958 Lang 18l.5 3,039,439 6/1962 Murek 91-25 3,048,8168/1962 Lubnow 181-.5 3,058,540 10/1962 Simpson 181-.5 3,118,348 1/1964Kline 9125 3,176,787 4/1965 Roever 181-.5 3,249,177 5/ 1966 Chelminski181.5 3,276,534 10/1966 Ewing et al. 181--.5 3,289,784 12/1966 Cassandet al. 181-.5 3,310,128 3/ 1967 Chelminski 181.5 3,322,232 5/1967Chalmers et a1 181.5

BENJAMIN A. BORCHELT, Primary Examiner.

W. KUJAWA, Assistant Examiner.

